Disk drives are widely used in computers and data processing systems for storing information in digital form. These disk drives commonly use one or more rotating storage disks to store data in digital form. Each storage disk typically includes a data storage surface on each side of the storage disk. These storage surfaces are divided into a plurality of narrow, annular, regions of different radii, commonly referred to as “tracks”. Typically, an E-block having one or more actuator arms is used to position a data transducer of a transducer assembly proximate each data storage surface of each storage disk. The E-block is moved relative to the storage disks with an actuator motor. Depending upon the design of the disk drive, each actuator arm can retain one or two transducer assemblies.
The accurate and stable positioning of each transducer assembly near each data storage surface is critical to the transfer and retrieval of information from the disks. As a result thereof, vibration in the E-block and the transducer assembly can cause errors in data transfers due to inaccuracies in the positioning of the data transducers relative to the storage disks. This is commonly referred to as “off-track motion”. Additionally, extreme shock loads during shipping, handling, and/or installation of the disk drive can cause extreme vibration in the E-block and the transducer assemblies. The extreme vibration can cause the data transducers to overcome the suspension load force and leave the disk surface, resulting in a “slap” or “crash” when returning to the storage disk surface.
Because it is most economical to utilize all surfaces of the disks in a disk drive, the E-block which has the heads attached at the ends of each of its arms results in an asymmetry of the top and bottom arms with respect to the inner arms. The outer actuator arms retaining only one head are referred to as being “depopulated”. The inner actuator arms retaining two transducer assemblies are referred to as being “populated”. The depopulated actuator arms bend and flex at different frequencies than the populated actuator arms as a result of the asymmetrical nature of having only one transducer assembly coupled to the actuator arm. The result of this asymmetry is additional vibration modes and “off track” motion.
FIG. 1A is a top plan view which illustrates the vibration in a prior art E-block 10P and transducer assemblies 12P with force applied by an actuator motor (not shown). FIG. 1B is a side perspective view which also illustrates the vibration in the prior art E-block 10P and the transducer assemblies 12P with force applied by an actuator motor (not shown). The prior art E-block 10P in FIGS. 1A and 1B includes four actuator arms 14P and six transducer assemblies 12P. The upper most and lower most actuator arms 14P are depopulated while the middle two actuator arms 14P are populated. As a result of the asymmetrical design, the actuator arms 14P and the transducer assemblies 12P each react differently to force applied by the actuator motor and to shock loads to the disk drive.
FIGS. 2A–2C further highlight how the asymmetrical design effect the resonance characteristics of the actuator arms and/or the transducers. For example, FIG. 2A illustrates a computer simulation of the off track motion for each data transducer 16P after force applied by the actuator motor for the E-block illustrated in FIGS. 1A and 1B. FIG. 2B illustrates a computer simulation of the G's to unload as a function of shock duration for the E-block illustrated in FIGS. 1A and 1B. Stated another way, FIG. 2B illustrates the G's required to lift the transducer away from the surface of the storage disk for a given shock duration. In FIG. 2B, the curve designated 18P illustrates the movement of the transducer on the depopulated actuator arm while the curves designed 20P each illustrate movement of the transducer for a populated actuator arm. FIG. 2C illustrates the amount of arm deflection for the actuator arms 14P of the E-block 10P as a function of shock duration for the E-block illustrated in FIGS. 1A and 1B. More specifically, in FIG. 2C, curve designated 22P represents the movement of the actuator arm which does not include any transducer assemblies, curve designated 24P represents the movement of the actuator arm with a single transducer assembly, and curve designated 26P represents the movement of the actuator arm having two transducer assemblies attached to the actuator arm.
One attempt to eliminate the effect of the depopulated actuator arms includes attaching a transducer assembly to each side of each actuator arm so that each arm is populated and adding an additional storage disk to the disk drive. However, the two additional transducer assemblies and the additional storage disk increase the cost for the disk drive and take up valuable space in the disk drive. Alternately, to maintain symmetry of the E-block, a three arm E-block with six transducers could be used in place of the four arm E-block. With this design, one extra disk would be required and two surfaces, the outermost surface on the outermost disks, would not be utilized.
Another attempt to minimize off track vibration and head slap includes cantilevering a mass in the form of a dummy swage plate from each depopulated actuator arm. The dummy swage plate can be effective in adding the additional mass to the system. However, the dummy swage plate increases the inertia of the E-block. This results in increased data seek times for the disk drive because the actuator motor is not able to move the E-block as quickly. Further, the dummy stage plate typically has different dynamic behavior and stiffness since it is not practical to make one the full transducer assembly length. Typically, short, simple shaped cantilever beams or swage bases are used. Additionally, the dummy swage plate is somewhat difficult to properly position and attach to the depopulated actuator arm. This adds extra components to the disk drive and increases the manufacturing cost of the disk drive.
Yet another attempt to minimize vibration effecting head slap includes using resilient mounts to secure the disk drive. The resilient mounts flex to attenuate shock and reduce head slap. Unfortunately, the resilient mounts also reduce disk drive performance during a data seek request.
In light of the above, it is an object of the present invention to provide a stable E-block having one or more depopulated actuator arms for a disk drive and method for making the same. Another object of the present invention is to provide an E-block having improved vibration and resonance characteristics, which does not degrade the performance of the disk drive. Still another object of the present invention is to provide an E-block which minimizes head slap and reduces drive fragility to shipping, handling, and installation. Yet another object of the present invention is to provide an E-block which can be adapted to be used with disk drives having an alternate number of storage disks. Still another object of the present invention is to provide an E-block having one or more depopulated actuator arms, which is relatively easy and inexpensive to manufacture.